Casing wear band and method of attachment

ABSTRACT

A crimpable wear band ( 105 ) tool has been invented for installation on casing ( 6 ), used in well bore drilling. A wear band ( 105 ) is provided having a cylindrical body which when coaxially placed over a pipe and substantially radially inwardly displaced at a plurality of points (i.e. crimped) about the circumference of a section of cylindrical body, attaches to the pipe to create a connection having structurally significant axial and torque load transfer capacity. When crimped according to the methods of the present invention, the load transfer capacity of the connection between the wear band ( 105 ) tool and the pipe ( 6 ) can be arranged to substantially prevent significant relative movement of the wear band tool on the pipe under loads that may be encountered when using one or more of the pipes as components of a tubular string used for drilling or running the casing in to complete a well bore.

FIELD OF THE INVENTION

The present invention relates to wear bands for casing a method ofattachment to enable transfer of structurally significant axial andtorsional loads between the wear band and pipe.

BACKGROUND OF THE INVENTION

Within the context of petroleum drilling and well completions, wells aretypically constructed by drilling the well bore using one tubularstring, largely comprised of drill pipe, then removing the drill pipestring and completing by installing a second tubular string, referred toas casing, which is subsequently permanently cemented in place. Theinstallation of casing, in this typical construction requires that thecasing be run into long boreholes, some having horizontal stretches. Inthese horizontal stretches, the casing must be installed by pushing italong the borehole. In so doing the casing is pushed in engagement withthe borehole wall.

Recent advances in drilling technology have enabled wells to be drilledand completed with a single casing string, eliminating the need to‘trip’ the drill pipe in and out of the hole to service the bit and makeroom for the casing upon completion of drilling. This change ismotivated by potential cost savings arising from reduced drilling timeand the expense of providing and maintaining the drill string, plusvarious technical advantages, such as reduced risk of well caving beforeinstallation of the casing.

However, casing installation through deviated wellbores or by drillingwith casing challenge the performance requirements of the casing.Installation can place severe structural demands on casing since theymust survive extended periods of time in contact with the borehole wall.

A device is needed to facilitate installation of casing either during astandard run in operation or when the casing is used for drilling.

SUMMARY OF THE INVENTION

A wear band tool has been invented for installation on casing, such aswould be useful in well bore drilling and casing operations. The presentinvention provides a wear band having a cylindrical body which whencoaxially placed over a pipe and substantially radially inwardlydisplaced at a plurality of points (i.e. crimped) about thecircumference of a section of the cylindrical body, attaches to the pipeto create a connection having structurally significant axial and torqueload transfer capacity. When crimped according to the methods of thepresent invention, the load transfer capacity of the connection betweenthe wear band tool and the pipe can be arranged to substantially preventsignificant relative movement of the wear band tool on the pipe underloads that may be encountered when using one or more of the pipes ascomponents of a tubular string used for drilling or completing wellbores.

The pipe on which the wear band tool of the present invention isinstalled must be capable of accepting the hoop stresses of crimpingwithout becoming unstable, for example, without buckling or crumpling.This generally requires that the pipe be thick-walled, for example,having an external diameter to thickness ratio (“D/t”) less than 100 andpreferably less than 50.

To be most generally useful for these applications, the wear band toolshould be amenable to rapid field installation on joints of pipe havingat least one non-upset end. In addition, the wear band tool, onceinstalled should not substantially reduce the minimum diameter (driftdiameter) through the pipe.

Thus, in accordance with a broad aspect of the present invention, thereis provided a wear band tool comprising: a body having an outer facingsurface and an inner bore therethrough sufficiently large to allowinsertion therethrough of a selected pipe having an external diameter,at least one tubular section on the body, the portion of the inner boreextending through the tubular section having an internal diametercapable of loosely fitting about the external diameter of the pipe and abearing surface on the outer facing surface.

The tubular section can be cylindrical or largely cylindrical with someradial variations to the internal diameter or outer surface. The tubularsection should be circumferentially continuous such that a hoop stresscan be set up by radially inwardly displacement (i.e. crimping) at aplurality of points about the circumference of the outer surface of thesection. The tubular section should be capable of accepting the hoopstresses of crimping without becoming unstable, for example, withoutbuckling or crumpling. This generally requires that the section bethick-walled, for example, having an external diameter to thicknessratio (“D/t”) less than 100 and preferably less than 50.

The loose fit of the section about the pipe must be sufficient toaccommodate the variations of the outer diameter of the pipe intended tobe used.

The bearing surfaces can be for example lines of weldments, hard-facedrings etc.

In accordance with the present invention there is also provided, amethod to attach a wear band tool to a pipe by crimping, the pipe havingan outer surface, such method comprising the steps of: providing a pipe;providing a wear band tool having a body with an inner bore therethroughsufficiently large to allow insertion therethrough of the pipe, aplurality of outward facing bearing surfaces on the body and at leastone tubular section on the body having an internal diameter capable offitting about the outer surface of the pipe; inserting the pipe throughthe inner bore of the wear band tool, applying an inward, substantiallyradially-directed force to a plurality of points about an outercircumference of the tubular section causing it to plastically deforminwardly and come into contact with the outer surface of the pipe,applying such additional inward, substantially radially directed forceas required to force both the wear band tool and the outer surface ofthe pipe to displace inwardly an amount at least great enough so thatwhen the force is released, an interference fit is created between thewear band tool and the pipe.

Preferably, the inward, substantially radially directed force is not sogreat that the drift diameter of the pipe is excessively reduced.Frictional forces enabled by the interference fit at the inwardlydisplaced section provide the mechanism by which structurallysignificant axial and torsional load may be transferred between the wearband tool and pipe without slippage therebetween.

The ability of the crimping method to ensure a residual interference fitis dependent on appropriate selection of various parameters as will beapparent to one skilled in the art. Where the application permits, fromthe point where plastic deformation of the wear band tool induced duringcrimping has reduced the original loose fit to come into contact withthe pipe of the method, differential temperature may be used to controlinterference according to the well known methods of shrink fitting,whereby the differential temperature is obtained by heating the wearband tool, cooling the pipe, or both, prior to crimping.

However, for the present application it is preferable to avoid therequirement to either heat the wear band tool or cool the pipe asrequired to obtain interference by shrink fitting. The method providesfor sufficient interference in the crimped connection through mechanicalmeans, without requiring a significant temperature differential betweenthe wear band tool and pipe at the time of crimping. This is realized byselecting the elastic limit of the wear band tool material, in thesection to be crimped, to be less than that of the pipe on which thewear band tool is to be installed. In this context, the elastic limitgenerally refers to the strain at which the material of the partsyields. Having the material properties thus selected, it will beapparent to one skilled in the art, that when the radial displacementapplied during crimping is sufficient to force the hoop strain of thepipe to be at least equal to its elastic limit, upon release of the loadcausing the radial displacement, the pipe will tend to radially ‘springback’ an amount greater than the wear band tool, were both partsseparated. Since the parts are not separated, the difference in thisamount of spring back is manifest as interference and fulfills thedesired purpose of creating interference by purely mechanical means.

While a purely mechanical method of obtaining interference throughcrimping is desirable for most applications, the present invention alsoanticipates applications where thermal and mechanical methods can becombined.

To facilitate the frictional engagement of the crimped wear band tool tothe thick-wall pipe the inside surface of the wear band tool, at leastover the section to be crimped, or the outer surface of the casing canbe provided with a roughened surface finish. In a further embodiment, afriction enhancing material such as a grit epoxy mixture is disposed inthe interfacial region of the crimped section. Similarly, variousbonding materials can be disposed in the interfacial region prior tocrimping to act as glues augmenting the frictional aspects of theconnection once their shear strength is developed after setting.

BRIEF DESCRIPTION OF THE DRAWINGS

A further, detailed, description of the invention, briefly describedabove, will follow by reference to the following drawings of specificembodiments of the invention. These drawings depict only typicalembodiments of the invention and are therefore not to be consideredlimiting of its scope. In the drawings:

FIG. 1 is a perspective view of a wear band tool according to thepresent invention;

FIG. 2 is a perspective view of the wear band tool shown in FIG. 1placed on a joint of casing as it might appear before crimping;

FIG. 3 is a partial sectional schematic view through the wall of a wearband tool positioned coaxially on a casing joint and inside a colletcrimping tool prior to application of radial crimping displacement;

FIG. 4 is the partial sectional schematic view of the assembly shown inFIG. 3 as it would appear after application of radial crimpingdisplacement; and

FIG. 5 is an axial sectional view of another wear band tool according tothe present invention crimped onto a joint of casing.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention, a wear band tool is provided asshown in FIG. 1, and a method of crimping it to a thick-wall metal pipewhen placed on the pipe as shown in FIGS. 2 to 4.

Referring to FIG. 1, a metal body 101 containing an internal bore 102, acylindrical mid-section 103 forming a section suitable for crimping, andtwo end intervals 104 on which hard-faced wear bands 105 are placed. Asshown, a concentric wear band 105 is placed at each end of the wear bandtool forming slightly raised diameter intervals. These wear bands areformed by attaching hard-facing material as commonly known to theindustry to metal body 101. The wear bands are selected to act asbearing surfaces and can withstand wear to a greater degree than theremainder of the wear band tool, the casing and casing couplers.

The cylindrical mid section and the end intervals are formed integral onthe body and the internal bore passes through all of them. While thecrimpable section in the illustrated embodiment is the cylindricalmid-section, it is to be noted that the crimpable section can be formedat one end, if desired. Also, it is to be noted that more than onecrimpable section can be provided on the wear band tool, as desired.

Wear bands should be selected with consideration as to the diameter ofthe borehole in which the wear band tool is to be used, such that thewear bands do not extend the full diameter of the borehole. Thisprovides that the wear bands do not block fluids passing up the annulusbetween the casing and the borehole wall.

The internal bore 2 of the wear band tool body is selected to looselyfit over at least one end of a casing joint 6 in FIG. 2. As shown, thisallows the wear band tool to be readily inserted over an end of the pipe6 and placed somewhere along the length of the pipe joint prior tocrimping. Thus placed, the method of the present invention in itspreferred embodiment provides a means to obtain a significantinterference fit after crimping even where the wear band tool and casingmaterial are at similar temperatures prior to crimping. In applicationswhere significant heating of the pipe and wear band tool, after wearband tool installation, is anticipated, the wear band tool is preferablyselected to have a thermal expansion coefficient that is equal to orless than that of the casing. Similarly in applications where coolingsubsequent to crimping is anticipated, the opposite relationship betweenthermal expansion coefficients is preferred.

Radial displacement required to crimp the wear band tool cylindricalmid-section 103 to the casing joint 6, on which it is placed, may beaccomplished by various methods such as by hydroforming, as described inCanadian application 2,328,190, filed Dec. 14, 2000. However, a fixtureemploying a tapered ‘collet in housing’ architecture has been found towork well in practice. This method of applying uniform radialdisplacement, and consequently radial force when in contact with theexterior of a cylindrical work piece surface, employs a device as shownschematically in FIG. 3. The device retains the externally taperedfingers or jaws 7 of a collet (segments of an externally conical sleeve)inside a matching internally tapered solid housing 8. Application ofaxial setting force to the housing 8, as shown by vector F, which isreacted at the face 7 a of the collet jaws 7, as shown by vector R,tends to induce the collet jaws 7 to penetrate into the collet housing 8along the angle of its conical bore. This causes the jaws 7 to moveradially inwardly and engage the work piece to be gripped, in thepresent case, shown as the cylindrical mid-section 103 of a wear bandtool. (Alternately, the action of the collet may be described in termsof setting displacement, understood as axial displacement of the collethousing 8 with respect to the collet jaws 7. In this case the settingforce is understood to arise correlative with the setting displacement.)The axial force F and reaction R are readily applied by, for example, ahollow bore hydraulic actuator (not shown), arranged with an internalbore greater than the casing 6 outside diameter.

With this arrangement, upon application of sufficient force (F), thejaws may be forced inward to first cause sufficient radial displacementto plastically deform the wear band tool cylindrical mid-section 103 andbring it into contact with the casing 6. This amount of radialdisplacement removes the annular clearance of the loose fit initiallyrequired for placing and positioning the wear band tool on the casing 6.Application of additional setting force then forces both the wear bandtool cylindrical mid-section 3, and the underlying wall of the casing 6,inward. In the preferred embodiment, the setting displacement ispreferably applied until the hoop strain in the casing wall at the crimplocation equals or slightly exceeds its elastic limit. It will beapparent to one skilled in the art that radial displacement beyond thispoint will cause little increase in residual interference but will havethe effect of reducing the drift diameter of the casing joint 6. FIG. 4schematically shows the collet, wear band tool and casing as they mightappear in the fully crimped position. After the desired radialdisplacement is achieved, the setting displacement of the collet isreversed which releases it from the wear band tool allowing the colletto be removed, leaving the wear band tool crimped to the casing.

To ensure that this method of cold crimping (i.e., mechanical crimpingunassisted by thermal effects) results in sufficient residualinterference between the wear band tool cylindrical mid-section 103 andthe casing 6, in its preferred embodiment the wear band tool material atthe cylindrical mid-section 103 has an elastic limit less than that ofthe casing 6. As is typically the case, the wear band tool and casingmaterial are both made from carbon steel having nearly the same elasticmodulii. Therefore, the elastic limit may be expressed in terms of yieldstrength, since elastic limit is generally given by yield stress dividedby elastic modulus.

However, in certain applications it may be desirable to further enhancethe load transfer capacity of a wear band tool attached to casing,without increasing the crimped length, by improving the frictionalengagement achieved for a given level of interference. While this may beaccomplished by various means, roughening one or both of the cylindricalmid-section inner wall or the casing outer surface on which the wearband tool was to be crimped, was found to be particularly effective.

The length of the section crimped will in general linearly affect theload transfer capacity of the crimped connection. For wear band toolsattached to full length casing joints, the length of the sectionsuitable for crimping, provided by the cylindrical mid-section 103 maybe extended almost without limit. Similarly the length of the colletjaws 7, do not limit length that may be crimped. The collet tool may beused to apply the required radial displacement at multiple axiallocations to incrementally crimp an extended length cylindricalmid-section 103. Increased load transfer capacity may thus be readilyachieved by increasing the crimped section length.

Referring to FIG. 5, another wear band is shown crimped on a casingjoint. The wear band facilitates installation of casing and includes ametal body 101 containing an internal bore 102, a cylindrical endsection 106 forming a section suitable for crimping, and an interval 104on which a wear band 105 is securely mounted. An end 108 of the wearband tool is ramped to facilitate passage thereover of discontinuitiesin the borehole. End 108 has a leading edge ramp angle α between theramped surface and the surface 9 of the inner bore that is selected toease movement of the casing through the borehole by reducing drag of thecasing and casing connections as the casing is advanced through theborehole, especially in horizontal sections, where the casing liesagainst the borehole wall. Generally, the angle α is selected to be lessthan about 60° and preferably less than 45° and most preferably lessthan about 20°. This ramped leading edge is preferably positioned facingdownhole to facilitate run in of the casing joint on which it ismounted.

The wear band tool can also be used downhole of a shoulder on thecasing, such as a coupling, wherein the ramped leading edge 108 canfacilitate passage of the casing through the borehole by preventing thecasing shoulder from digging into the formation. The wear band tool can,therefore, be used alone to space the casing from the borehole wall andto accommodate wear, since the wear band 105 will wear preferentiallyover the shoulder on the casing.

It will be apparent that these and many other changes may be made to theillustrative embodiments, while falling within the scope of theinvention, and it is intended that all such changes be covered by theclaims appended hereto.

1. A method for attaching a wear band tool to a pipe by crimping, thepipe having an outer surface, such method comprising the steps of:providing a pipe; providing a wear band tool having a body with an innerbore therethrough sufficiently large to allow insertion therethrough ofthe pipe, at least one outward facing bearing surface on the body and atleast one tubular section on the body having an internal diametercapable of fitting about the outer surface of the pipe; inserting thepipe through the inner bore of the wear band tool, applying an inward,substantially radially-directed force to a plurality of points about anouter circumference of the tubular section causing it to plasticallydeform inwardly and come into contact with the outer surface of the pipeat points corresponding to the plurality of points; and applying suchadditional inward, substantially radially directed force as required toforce both the wear band tool and the outer surface of the pipe todisplace inwardly an amount at least great enough so that when released,an interference fit is created between the wear band tool and the pipe.2. The method of claim 1 wherein at least one of the outer surface ofthe pipe and an inner surface of the tubular section is roughened tofacilitate frictional engagement therebetween.
 3. A wellbore casingassembly comprising: at least a section of well bore casing; and awellbore casing wear band tool crimped onto the at least a section ofwell bore casing, the wellbore casing wear band tool including: a bodyhaving a first end and a second end opposite the first end, an outerfacing surface and an inner bore extending therethrough from the firstend to the second end sufficiently large to allow insertion therethroughof the external diameter of the well bore casing, at least one crimpabletubular section on the body through which the wellbore casing wear bandtool is crimped about the external diameter of the well bore casing anda bearing surface on the outer facing surface.
 4. The wellbore casingassembly of claim 3 wherein the bearing surface being selected towithstand wear to a greater degree than the remainder of the wear bandtool.
 5. The wellbore casing assembly of claim 3 wherein the crimpabletubular section has an external diameter to thickness ratio of less than100.
 6. The wellbore casing assembly of claim 3 wherein the crimpabletubular section has an external diameter to thickness ratio of less than50.
 7. The wellbore casing assembly of claim 3 wherein the crimpabletubular section is circumferentially continuous such that hoop stresscan be generated therein.
 8. The wellbore casing assembly of claim 3wherein the bearing surface includes a ramped end.